On 2013-12-12, Rob <nom...@example.com> wrote: > Jan Ceuleers <jan.ceule...@computer.org> wrote: >> Interesting Light Reading article on the degree to which infrastructure >> (in casu wireless networks) is dependent on GPS timing signals, how >> little is needed to jam GPS (intentionally or otherwise), and what the >> impact of such jamming would be. >> >> It also talks about how PTP might or might not mitigate some of these >> issues. >> >> http://www.lightreading.com/mobile/mobile-security/were-jamming-gps-weakness-could-sink-wireless/d/d-id/706895 > > It depends on the structure of the network and the required accuracy. > Remember that the usual GPS jamming methods are quite local in nature. > > You can jam my GPS but that won't take out my DCF77 receiver or the > three GPS-synced servers I have configured as internet NTP sources.
If they are in the same locality (or, depending on the strength of the jamming, local could mean within a few Km) they could also be jammed. Also, transmitting time via a network (whetehr wired or radio) can have a fair amount of jitter so it depends on the accuracy that the wireless towers need. If it is seconds no problem. If it is nanoseconds, you just won't get that. > Nor will it take out my peer server that itself has DCF77 and some > other internet time sources, that are again synced to different other > servers. > > Of course it is possible to jam everything, just not very likely. The article talks about a truck driving by the airport (ie a few km) jamming the airport. And that was a trucker probably unwilling to spend more than a 100 dollars on his jamming gear. > In a mobile network, it should be possible to get time information > both from the local GPS receiver and via the glass/microwave link > as a backup. But does it have the required accuracy? I do not know. _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions